The present invention relates to the display of communication signal information, and more particularly to a time history display of orthogonal code power levels by spreading factor.
There are various methods for displaying the power of orthogonal codes in a code division multiple access (CDMA) signal. In a COMA signal using orthogonal codes, all of which are the same length (also known as spreading factor), the amount of power present in each code, i.e., code domain power (CDP), may be displayed by plotting the power in each code versus the code number index on a two-dimensional graph. This is a conventional and well-understood manner using linear index code order for displaying CDP information. Newer CDMA systems, such as cdma2000, now specify use of codes of varying spreading factors, i.e., of different lengths, which complicates the display of CDP. Specifically codes of smaller spreading factor when displayed in a CDP graph appropriate for the largest spreading factor code appear dispersed into multiple sub-codes at fixed distances determined by their relationship to the larger spreading factor code system, i.e., a code with a spreading factor of 16 when displayed on the code graph for a spreading factor of 128 has 8 sub-codes spaced 8 indices apart. Also the total code power of the lower spreading factor code is not correctly indicated by the power levels of the individual sub-codes. Both of these factors cause difficulty in interpreting the results of CDP calculations when codes of different spreading factor values are present.
U.S. Pat. No. 6,219,340 describes one method of displaying power levels for a CDMA signal having orthogonal codes with different spreading factors or code layers. In this display a power level for each active code channel is displayed using a vertical bar, with the width of the bar indicating in which code layer each active code channel is active. However this display does not highlight the relationship of sub-codes to the base code. This deficiency is remedied by co-pending U.S. patent application Ser. No. 09/919,690 filed Jul. 31, 2001 in which the relationship of sub-codes to the base code is indicated by using two graphs, one of which is in bit-reversed index code order to group the sub-codes of lower spreading factors together. Additionally a base code power indicator in the form of a horizontal bar extends across the sub-codes in the graph using Walsh code order, representing the spreading factor for the base code at a level representing the base code power. Another display method is disclosed in co-pending U.S. patent application Ser. No. 09/967,555 filed Sep. 28, 2001 in which a third dimension is used in the display of code domain power for orthogonal codes having different spreading factors.
These methods allow a user to see at any point in time which codes are active and at what power levels. Some methods also provide visualization of base code to sub-code relationships and spreading factors. However the nature of a live signal makes it very difficult to determine from a code power graph when the various codes become active and inactive, how widely distributed the various spreading factors are, or how to spot trends such as under-active and over-active codes because the graph updates many times per second, showing different data each time.
U.S. Pat. No. 4,870,348 describes a quasi-3-dimensional display referred to as a color spectrogram which shows a number of frequency spectra that were generated over time as a series of colored lines where color is used as a substitute for a third dimension. Each single line is a complete spectrum, with different frequencies being represented by different points along the line and the color of each point representing an amplitude at that frequency. This display has a pseudo-random, evenly-divided x-axis with a data resolution that is usually the same or greater than the display pixel resolution and that doesn't vary from one spectrum record to the next.
What is desired is a method of displaying a time history of orthogonal code power levels by spreading factor to allow users to quickly spot trends and determine timing relationships.